一般说来，ANSYS的流固耦合主要有4种方式：1，sequential这需要用户进行APDL编程进行流固耦合sequentia指的是顺序耦合以采用MpCCI为例,你可以利用ANSYS和一个第三方CFD产品执行流固耦合分析。
在这个方法中，基于网格的平行代码耦合界面(MpCCI) 将ANSYS和CFD程序耦合起来。
即使网格上存在差别，MpCCI也能够实现流固界面的数据转换。
ANSYS CD中包含有MpCCI库和一个相关实例。
关于该方法的详细信息，参见ANSYS Coupled-Field Analysis Guide中的Sequential Couplin2，FSI solver流固耦合的设置过程非常简单，推荐你使用这种方式3，multi-field solver这是FSI solver的扩展，你可以使用它实现流体，结构，热，电磁等的耦合4，直接采用特殊的单元进行直接耦合，耦合计算直接发生在单元刚度矩阵一个流固耦合的例子length=2width=3height=2/prep7et,1,63et,2,30 !选用FLUID30单元，用于流固耦合问题r,1,0.01mp,ex,1,2e11mp,nuxy,1,0.3mp,dens,1,7800mp,dens,2,1000 !定义Acoustics材料来描述流体材料-水mp,sonc,2,1400mp,mu,0,!block,,length,,width,,heightesize,0.5mshkey,1!type,1mat,1real,1asel,u,loc,y,widthamesh,allalls!type,2mat,2vmesh,allfini/soluantype,2modopt,unsym,10 !非对称模态提取方法处理流固耦合问题eqslv,frontmxpand,10,,,1nsel,s,loc,x,nsel,a,loc,x,lengthnsel,r,loc,yd,all,,,,,,ux,uy,uz,nsel,s,loc,y,width,d,all,pres,0allsasel,u,loc,y,width,sfa,all,,fsi !定义流固耦合界面allssolvfini/post1set,firstplnsol,u,sum,2,1fini再给大家一个实例！考虑结构在水中的自振频率：例子是一加筋板在水中的模态分析。
命令流如下：FINISH/CLEAR/FILENAME,plane/UNITS,SI/TITLE,plane/PREP7!*********ELEMENT DEFINE********ET,63,63ET,4,beam4et,30,fluid30!****MATERIAL DEFINE*********MP,EX,1,2.10E11MP,DENS,1,7850MP,NUXY,1,0.3mp,dens,30,1025mp,sonc,30,1500mp,mu,30,0.5!*******REAL CONSTANT***********r,30,1e-06r,50,0.05r,75,0.375e-02,0.78125e-06,0.000016406k,1k,4,1kfill,1,4,2,,1kgen,4,1,4,1,,1/3,,10a,1,2,12,11*do,i,0,2*do,j,0,2*10,10a,1+i+j,2+i+j,12+i+j,11+i+j*enddo*enddo!***************************fluid element****************k,100,-14.5,-14.5k,101,-14.5,15.5k,102,15.5,15.5k,103,15.5,-14.5k,140,-14.5,-14.5,30k,141,-14.5,15.5,30k,142,15.5,15.5,30k,143,15.5,-14.5,30a,100,101,102,103,4,14,24,34,33,32,31,21,11,1a,1,2,3,4,103,100a,140,141,142,143a,100,101,141,140a,101,102,142,141a,142,143,103,102a,140,143,103,100a,14,24,34,33,32,31,21,11,1,2,3,4asel,u,,,1,FLST,2,8,5,ORDE,FITEM,2,FITEM,2,V A,nummrg,allallsMSHKEY,0 MSHAPE,0esize,1lsel,s,loc,y,1/3lsel,r,loc,x,0,1lsel,r,loc,z,0latt,1,75,4lmesh,alllsel,s,loc,y,2/3lsel,r,loc,x,0,1lsel,r,loc,z,0latt,1,75,4lmesh,alllsel,s,loc,x,1/3lsel,r,loc,y,0,1lsel,r,loc,z,0latt,1,75,4lmesh,alllsel,s,loc,x,2/3lsel,r,loc,y,0,1lsel,r,loc,z,0latt,1,75,4lmesh,allasel,s,,,1,9aatt,1,50,63amesh,allallsMSHAPE,1,3desize,3vsel,s,,,1type,30 $mat,30 $real,30 vmesh,allallsFINISH/solualls!**** 求解***********!********************* ANTYPE,MODAL MODOPT,lanb,25,0 SOLVEFINISH总是出现error 说矩阵不对称，不可以用lanb计算。
总结：流体单元不能用对称的解法应该采用非对称解法。
例子是一圆环在水中的模态分析。
命令流如下：finish/clear/PREP7!定义单元类型ET,1,PLANE42 ! structural elementET,2,FLUID29 ! acoustic fluid element with ux & uyET,3,129 ! acoustic infinite line elementr,3,0.31242,0,0ET,4,FLUID29,,1,0 ! acoustic fluid element without ux & uy !材料属性MP,EX,1,2.068e11MP,DENS,1,7929MP,NUXY,1,0MP,DENS,2,1030MP,SONC,2,1460! 创建四分之一模型CYL4,0,0,0.254,0,0.26035,90CYL4,0,0,0.26035,0,0.31242,90! 选择属性,网格划分ASEL,S,AREA,,1AA TT,1,1,1,0LESIZE,1,,,16,1LESIZE,3,,,16,1LESIZE,2,,,1,1LESIZE,4,,,1,1MSHKEY,1MSHAPE,0,2D ! mapped quad meshAMESH,1ASEL,S,AREA,,2AA TT,2,1,2,0LESIZE,5,,,16,1LESIZE,7,,,16,1LESIZE,6,,,5LESIZE,8,,,5MSHKEY,0MSHAPE,0,2D ! mapped quad meshAMESH,2! 关于Y轴镜像nsym,x,1000,all ! offset node number by 1000 esym,,1000,all! 关于y轴镜像nsym,y,2000,all ! offset node number by 2000 esym,,2000,allNUMMRG,ALL ! merge all quantitiesesel,s,type,,1nsle,sesln,s,0nsle,sesel,invensle,semodif,all,type,4esel,allnsel,all! 指定无限吸收边界csys,1nsel,s,loc,x,0.31242type,3real,3mat,2esurfesel,allnsel,all! 标识流固交接面nsel,s,loc,x,0.26035esel,s,type,,2sf,all,fsi,1nsel,allesel,allFINISH/soluantype,modalmodopt,damp,10mxpand,10,,,yessolvefinish为了便于对比，也对圆环在空气中做了模态分析finish/clear/PREP7!定义单元类型ET,1,PLANE42 ! structural element!材料属性MP,EX,1,2.068e11MP,DENS,1,7929MP,NUXY,1,0! 创建四分之一模型CYL4,0,0,0.254,0,0.26035,90! 选择属性,网格划分ASEL,S,AREA,,1AA TT,1,1,1,0LESIZE,1,,,16,1LESIZE,3,,,16,1LESIZE,2,,,1,1LESIZE,4,,,1,1MSHKEY,1MSHAPE,0,2D ! mapped quad meshAMESH,1! 关于Y轴镜像nsym,x,1000,all ! offset node number by 1000esym,,1000,all! 关于y轴镜像nsym,y,2000,all ! offset node number by 2000esym,,2000,allNUMMRG,ALL/soluantype,modalmodopt,lanb,10mxpand,10,,,yessolvefinish在水中的自振频率为SET TIME/FREQ LOAD STEP SUBSTEP CUMULATIVE 1-0.19544E-10 1 1 12 0.29640E-03 1 1 13-0.21663E-10 1 2 24-0.29640E-03 1 2 25 0.30870E-03 1 3 36 0.0000 1 3 37-0.30870E-03 1 4 48 0.0000 1 4 49-0.53726E-03 1 5 510 0.57522E-11 1 5 511 0.53726E-03 1 6 612-0.89057E-11 1 6 613 0.98059E-01 1 7 714 35.232 1 7 715 0.98059E-01 1 8 816 -35.232 1 8 817 0.98061E-01 1 9 918 35.233 1 9 919 0.98061E-01 1 10 1020 -35.233 1 10 10在空气中的自振频率为SET TIME/FREQ LOAD STEP SUBSTEP CUMULATIVE1 0.0000 1 1 12 0.0000 1 2 23 0.73609E-03 1 3 34 60.805 1 4 45 60.805 1 5 56 172.97 1 6 67 172.97 1 7 78 334.40 1 8 89 334.40 1 9 910 546.59 1 10 10主要有以下疑问：1）考虑流固耦合，做模态分析时流体单元是否只能用fluid29（2d）和fluid30（3d),对于fluid129和fluid130在耦合中具体起到什么作用，能不能不设，而用边界约束条件代替？2）流体范围怎样确定，如本例中（CYL4,0,0,0.26035,0,0.31242,90），外半径为0.31242。